This invention relates generally to radiographic inspection and more particularly to digital radiography of certain airframe structures.
In addition to a fuselage, the airframe of a typical aircraft includes the main wings and an empennage (tail assembly), and the flight control surfaces (e.g., flaps, ailerons, elevators and rudders) thereof. These airfoil structures are typically constructed of a honeycomb core material covered by a thin skin of a lightweight material. Over time, the honeycomb material can develop defects that, if left undetected, could threaten the structural integrity of the airfoil structure. In addition, moisture and other foreign objects can become entrapped in the airfoil structures and detract from the overall performance of the aircraft.
For these reasons, the airfoil structures usually undergo routine inspections. Film radiography is a common nondestructive testing technique for inspection of wings, empennage and flight control surfaces. A typical approach to film radiography of large horizontal and vertical surfaces of an aircraft is to lay numerous sheets of x-ray film in a mosaic pattern across the surfaces to be inspected. An x-ray source is then positioned on the opposing side of the structure and at an appropriate distance to simultaneously expose the films to radiation. The films are then removed and developed. The developed film can then be examined to determine if any flaws exist in the imaged structure.
With this approach, each film must be physically placed in position, exposed, removed, moved to a processor, developed, moved to a light box for review, and then physically moved to archive. Film radiography of large airfoil structures is thus time consuming, labor intensive and costly. This technique also requires a large amount of film and processing chemicals that must be properly disposed. Furthermore, the images are not available for review until after the film has been developed. This means that if an error occurred in the exposure of the film, or if the inspector wishes to obtain a different or more detailed view of a certain portion of the airfoil structure, then the entire process must be repeated again to obtain the new or corrected images. Accordingly, it would be desirable to have a method and system for inspecting airfoil structures on aircraft that provide instantaneous or real time images without the time and expense of film radiography.
The above-mentioned need is met by the present invention, which provides a system and method for radiographic inspection of airfoil structure on aircraft. This system includes a radiation source located on one side of the airfoil structure and an X-Y scanning device located on an m opposing side of the airfoil structure. The X-Y scanning device is positioned to receive radiation from the radiation source. A radiation detector is mounted on the X-Y scanning device so as to be moveable relative to the airfoil structure along two mutually orthogonal axes. In operation, the radiation detector is moved in a predetermined raster pattern while the radiation source is emitting radiation. The radiation detector converts impinging radiation into electrical signals, and a computer system processes the signals to generate radiographic images of the airfoil structure.